Re: undoing something

"John Dlugosz" [off-list ref] writes:

I made a mistake.  Big deal, now that I know that git storage is
immutable and changes just add to what's already there.  

A quick look at
	git reflog show topic
tells me that {1} is the one I want.  So, how do I rewind branch topic
to point to topic@{1} ?
I did it by making a tag, and then in gitk pointing to it and picking
"reset to here" from the context menu.  

A while back I was looking for the right/easy way to simply repoint my
branch to where I wanted.  The best answer was to use push.

The answer was best only because in your previous question you wanted to
ensure fast-forwardness, i.e. "git push . origin/dev:dev" without plus in
front to cause it to fail if it is not fast-forward.

If you know you have one unwanted commit you would want to discard at the
tip of topic, you do not want fast-foward safety to kick in.

 (1) if you are on the topic branch, you can say "git reset --hard HEAD^";
     or

 (2) if you are not, you can obviously check out topic and do the above,
     or "git branch -f topic topic^".

If the garbage you have at the tip of the topic is not just a single
commit, you can replace HEAD^ and topic^ in the above with whatever commit
you would want to point the tip at.